Palaeontology Department Seminar
Chert on the beach
Dr. Lil Stevens,
Department of Palaeontology, NHM
Thursday 1st March
Neil Chalmers Seminar Room, DC2,
16:00 - 17:00
In 2004 an amateur collector found a dull brown cobble on the beach at Sandsend, part of the Yorkshire Jurassic coast. Hammer at the ready, he broke the cobble into eleven pieces and looked into its interior. It was probably raining, which would have helped him to see small pieces of fossilised plants preserved within the chert, including what looked like reproductive structures. The cobble made its way to Birmingham University and after many months of sectioning and polishing, there began to emerge the most beautifully preserved Palaeozoic plant and crustacean remains I have ever seen.
Contained in the cobble were vegetative and reproductive fragments of an arborescent lycopsid with cellular preservation. The cone fragments were described as Flemingites arcuatus sp. nov. and analyses confirmed a provisional assignment to Paralycopodites stem genus. Associated with the plant remains were many small univalve crustaceans described as Ebullitiocaris elatus sp. nov., the same genus as those found in the Devonian Rhynie chert from Scotland. Extremely rarely for this age of fossil, both internal organs and appendages are visible and show a long morphological stasis and even some features still retained by modern Cladocera.
The cobble has preserved organisms of mid to late Carboniferous age and is therefore ex-situ. Chert content analysis and the level and mode of preservation of the fossils suggests not necessarily a hot spring environment, but a swamp certainly influenced by some sort of hydrothermal volcanic activity that caused rapid solidification. Comparison with other cherts has not helped to narrow down the original locality and it is thought that although the cobble was probably transported south east by glacial activity, it is also possible that it was dumped as ballast on the busy shipping routes around north east Britain, and so could have originated from almost anywhere in the world.
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